Cork product and process of making the same



C. H. SCHUH June 6, 1944.

CORK PRODUCTS AND PROCESS OF MAKING THE SAME Filed Aug. 7, 1941 .k Y m r. O0 W am n Patented June 6, 1944 UNITED STATES PATENT oFi-icE coltll rnonuml l lrl l llglssol' MAKING Charles n.

Carbide Schuli, Bldgewooil, N. 2., assignor to and carbon Chemicals corporation, a

corporation of New York Application August l, 1941, Serial No. 405,824

(Cl- 202-l8) .llOIaiml- This invention relates to the treatment of cork materials to obtain low density cork pieces useful, for instance. in insulation and. acoustical compositions and products, to the treated cork per se and to byroducts of said treatment.

.The invention particularly relates to cork granules having a pliable springy character and extremely low density and to a process of producing said cork granules utilizing as a medium of expansion and treatment a liquid bath, for instance of a moltenmetallic substance preferably comprising lead and which liquid medium is substantially non-absorbent and substantially non-adherent to cork and preferably substantially inert to cork and its decomposition products.

Molten metallic and other liquid baths have heretofore been employed for the destructive distillation of organic materials. For instance, it has been proposed to subject coal, wood, sawdust and shale to destructive distillation in metallic baths, lead containingbaths being amongstthose employed. The object of the treatment has been to obtain maximum distillation products and the solid residue substances have been by-products or waste products. Examination of such solid residues shows that the substances treated shrink in processing and become brittle, regardless of time and temperature of treatment. It has also been proposed to treat a mineral matter, for instance mica, in such alternative molten mediums as metal or glass to eilect an exfoliation of the mica material. Here again control of temperature and time of treatment, insofar as the solid residue is concerned, has not been a consideration, since mica is a mineral that can be subjected to heat for extended periods and to intense temperatures without adverse eilects, and in treating this substance once a temperature high enough for exfoliation has been reached the application of higher temperatures or long periods of treatment has no further efiect upon the material. 1

With respect to cork it has heretofore been proposed to expand pieces of natural cork by heating in a gaseous'medium, for instance superheated steam, and to compress the expanded pieces in a mold into a.unitary slab, the natural resins oi the cork binding the pieces together in the process. According to this procedure, the cork cells are expanded and the cork itself undergoes a loss in density due to the removal moisture and some decomposition volatile matter. In making molded cork slabs it has been further suggested that the pieces of natural cork be preheated in a receptacle to a temperature between 400 F. to 550 1''. or to bring the cork pieces to such temperatures in a lead metalliclbath to obtain an increase of volume between to 100 per cent. In this condition the cork pieces retain the relatively hard characteristics of natural cork theretofore used. Bubseq ntly the expanded pieces are compressed in mold and baked at the conventional-baking temperatures at or above 600 1''. while retaining the pieces under pressure to consolidate the pieces into unitary bonded slabs.

Insofar as expanding cork pieces in a liquid medium to obtain a large degree of expansion and very low densities without destruction of the cork is concerned, it is believed that these and other prior teachings have suggested this to be impossible. l'br instance, in United States Letters Patent 997,056 it is taught that the cork pieces should be treated at temperatures below 200 0. (392 F.) when subjected to a liquid bath, as the cork cells are flabby at a high temperature and cannot withstand the pressure or the column of liquid above such temperature. Moreover. Patent 997,056 indicates that when cork is boiled in water or linseed oil and resin that only small expansions are possible and that for any appreciable expansion a gaseous medium should be employed. a

In contrast to the prior teachings, I have discovered that with proper precautions and within the critical limitations hereinafter set forth cork pieces may be expanded in a non-absorbing liquid medium, for instance in a molten metallic bath preferably comprising lead, to an extent even considerably beyond that possible in a gaseous medium and wlth the obtaining of excellent residual properties. I have found that a regranulated cork of even more advantageous properties than that disclosed in my co-pending application Serial No. 271,202 may be made in this manner. The new process diifers completely from the process of treating natural cork waste as carried out in a retort or rapid heating of such material with an inert gas in a rotary kiln as described in said prior application, and is simple, quick, more eillcient and more economical. Regranulated cork obtained according to the present invention, moreover, permits new features of lower density and greater resiliency to I be given to the light weight compositions of such material described in said co-pending application.

Thus, it is amongst the objects of my invention II to produce expanded cork pieces by a treatment in a bath, substantially non-absorbent and nonnatural or other adherent relative. to cork, and to produce expansions of such' material even as high as 200 to 375 per cent .by volume where the raw material is natural cork. A further object is to produce expanded cork pieces havinga density of less than 2 pounds and even aslow asf l pounds per cubic foot'and which expanded cork pieces will have a substantial springy character, be soft distinguished from naturalcork and rubbery as I of j surface and will not possess suclran amount carbonization as will produce a brittle surface.

Another object is to produce an expanded cork material having a density between abouti2 and v 2 pounds per cubic foot and which cork will retain substantially 80% or more of the original volatile matter in the cork in natural air dried state. A further object is to produce cork granules having a density between 1 and 2 pounds per cubic foot and which-cork pieces will retain between about'60 toabout 80-per cent by weight of thevolatiles contained in the cork in natural air driedv form-,and will have inhibiting fungus growth when the property of combined in sufficient amount withorganic substances,.for instancecellulose. A further. object is to submerge cork pieces ina molten metallic bath, preferably consisting of lead, for a total period between about 40 seconds to about 4 minutes, the temperature of the bath being maintained between 580 F. to 720 F. but preferably between 620.F. and 680 F. Afurther object is to pretreat the natural cork or other cork pieces, before treatingina liquid bath as aforesaid, by boiling in water preferably for a period of about minutes to' about 30-minutes to cause said cork material to absorb tain maximum expansion of the cork pieces when treated in the liquid bath. 4

These and further. objects of the invention will,

tion. I y

In accordance with the have discovered 620 F., preferably within 20' temperature, as above about 655 F. cork pieces have a tendency to burn when removed from the moisture, to thereby 'ob-' bath and this tendency increases with higher temperatures; also above 655 F. surface car- .bonization of the cork pieces substantiaL. However, good results have also u been obtained with temperatures of the bath i'romabove 655 Etc aboutH680 F. (360 C.) burning-tendency; or over carmum expansion in the temperature range 620- 65 5 1?. in about 40 seconds. In this exceedingly short period of treatment about to by isweight jo'fthe cork ofvolatile and decomposition product will be 'very springy, much -more thannatura] cork; will be soft and'rubbery a combination of properties not characteristic of natural cork or of any expanded cork of which I .isfactorily'as a regranulated cork in compositions such as described in my co-pending appli- 10 cation aforesaid with improved results. The resultant cork, however, will not have the fungus growth inhibiting properties described in my copendingapplication aforesaid as an insufllcient amount of decomposition matter is formed in as this treatment. However, if treatment or the cork material in the bath be extended past 40 seconds to a'period up to about 3 to 4 minutes 40 ter will continue up to about 40% by weight of the In this range of treatment between about 25% and 40% by weight of the cork will constitute volatile and decomposition matter still removable andthe found, upon-division, about 1% and about This cork will also possess soft and rubbery properties and will, further, exhibit, fungus growth inhibiting properties. However, it is found that aking possible (Q the low limit not obtainbegins to become am aware, and will function satto have a density between 2 pounds per cubic foot.

point outside ofthe. temperature range is utilized. It is to be observed that the use of a lead bath is remarkable when considering the high pressure of this molten material against the expanding cells of the cork and the rapid removal of moisture and decomposition products made possible by such material, and in particular in view of the prior concepts held regarding the use of liquid baths generally in the treatment of cork material.

When the temperature of the bath falls below the melting point of lead (621 F.) such as becomes possible when a lead alloy, for example, is employed and the temperature is not brought up to the desired range, it becomes necessary to extend the period of treatment of the cork pieces to obtain the expanded material. It appears that the heat penetration substantially below such temperature is neither as rapid as that in the preferred range nor does the heat extend completely into the cork of the treated pieces unless the time interval of treatment be considerably extended with a resultant increase in carbonization at the surface and a product having less resiliency. In spite of this condition I have found that cork material of useful character but not as desirable as that obtained in the preferred temperature ranges of treatment is possible with baths having a temperature as low as 580 F. A useful product is also obtained in the temperature range above 680 F. to 720 F. (360 0.), but it has been found that above 680 F. excessive burning of the cork begins to take place. Accordingly, temperatures above 720 F. and below 580 F. should, therefore, be avoided. Also treatment should not exceed about 4 minutes.

The length of time within theprescribed limits to which the cork material is subject to the treatment will be somewhat dependent upon the grade of natural cork employed and the extent of moisture therein. Also the time treatment may be slightly increased when the cork pieces are of a size greater than given, say above about /4 inch. Thus, I have found it desirable in practicing the present invention to pretreat the cork by boiling the same in water for a period of about to about 30 minutes to obtain a maximum absorption of moisture therein, this generally taking place in the first few minutes. By this pretreatment a maximum expansion of the cork pieces in a minimum time of treatment may be obtained and the extent of carbonization be, accordingly, reduced to a negligible amount, if any at all. I have also observed that in the preferred temperature range the volume change in the cork for all periods above about.40 seconds treatment is substantially negligible, and that the optimum expansion of the cork occurs in this period of treatment regardless of whether or not the cork has been pretreated as described or a cork material previously somewhat heat treated is employed. I would have it understood that while I prefer to initiate the present process with natural cork pieces, cork pieces which may have been somewhat expanded by other processes may be utilized and be given the benefits of the present process to the extent that their initial condition permits. In some cases with cork of this character it will be found desirable to reduce the total time of treatment to obtain the desired results. Moreover, it will be understood that the percentages of volume change given are based upon natural cork and that, accordingly, when a pre-expanded cork is subjected to the present I U assoaaa able where an alloy or metal having a melting process it quite may not have a total expansion within the optimum'ilgures given.

It is sometimes foundin the present process that small quantities of metal where a metallic bath is employed .are mechanically carried out with the cork pieces even 'thollfll such material does not adhere thereto. I have found that this metal may be easily separated from the cork when the expanded cork pieces are ground and screened for use and more readily by subjecting the ground cork to flotation in water in which case any metal immediately settles to the bottom where it may be removed. If the cork material is to be utilized in the manner described in my co-pending application aforesaid. in conjunction with an aqueous, fibrous suspension the ground, treated cork may be directly mixed therewith as the metal particles will settle to the bottom of the receptacle in which the cork and fiber are mixed and may readily be removed. Accordingly, the step of removing foreign metallic particles is an added feature of the present invention.

For a better understanding of the presentinvention the following examples are given which are not in any manner to be considered as limiting the present invention:

Example No. 1

A lead bath is fitted with a funnel dipping slightly beneath the surface of the lead: the end of the funnel is fitted through a delivery tube to a condenser. A small wire cage is made with handle attached which can be held beneath the surface of the lead by suitable supporting means. and under the funnel. The cage is partially filled with granulated natural cork preferably between inch and $5 inch in size, allowing ample space in the cage for the material to expand without restriction. The cage containing the cork pieces is then held in the bath with the cork submerged for a period of about 40 seconds with the bath kept at a temperature of about 350 0. (662 F). During this treatment volatile matter boils oil through the lead and up through the funnel into the condenser where it is condensed and flows into a receiver. After 40 seconds the cage is removed from the lead and the treated cork pieces are taken from the cage. The operation is repeated until the desired quantity of treated cork is obtained. For the uses contemplated in my copending application aforesaid the treated cork pieces are then ground to ing through a 12 mesh screen and in such condition the regranulated cork will have a density of about 2.15 pounds per cubic foot. The material is dark brown in color and while it grinds easily compared to natural cork, it is very springy and not at all brittle. About 17% of. distillate is obtained based upon the weight of the natural cork and-this is almost entirely aqueous with very little oil. The distillate is dark reddish brown, has a strong characteristic odor and acid reaction and becomes darker upon standing. While the lead of the bath does not adhere to the cork in the processing, small quantities may be carried out with the cork pieces mechanically. Such may be easily separated as described above by grinding and floating the cork in water. Any lead, of course, then immediately settles to the bottom of the water and is separated.

Where it is desiredto obtain the treated cork product of the invention by a continuous procedure the raw material may instead of being placed in a wire cage be fed, as shown in the drawing, from a source of supply it, to a feed a size preferably passhopper i2, to a heating chamber M, Q viously the volatiles obtained in the processing chargedwithmolten lead to a level it. The maybecollected and condensed for further treatchamber ll, receivesitsyheat from I, furnace l.) ment; It will be understoodthat the chain 2 situated below the bath and the chamber-has agas-tight' cover or head 20, provided withan outlet II, from which the volatiiesof the cork material'may bewithdrawnvan'd conveyed to a connot shown, for further treatmentto obdenser,

tain the by products thereof; Within the chainher is a conveying device consisting of a pair of sprockets i2,

metallic bath. chain of thin metallic L shaped plates 28, secured'to thechain so that they project atright angles to the links thereof and dip into the metallic bath along the low run of the chain. The feed hopper is of a sizecapableof receiving asufllcient charge to last for a complete run and is provided with a gas-tight cover and port to prevent the escape of volatilesthrough this member. The low end .of the hopper II, has an'opening 28, entering into the chamber l4, and throughwhich the raw material drops upon the surface of the metallic bath and into operative contact with the plate members It, of the continuous chain. In the drawing the sprockets are indicated, to rotate direction so that the plates carried by suitable shafts supported f on suitable trunnions and a'chain or chains 24,

operating. immediately adjacent but not in the carries a multiplicity temperature of the characteristics would edges of the chain may-be provided with suitable shields for preventing the escape of the cork pieces out the ends of'the spaces formed between the' plate members. It is preferred that the depth of the plates be such that only a single layer of cork particles-be drawn by the plates below the surface of the bat At the opposite end of the chamberwhere the chain platesemerge from'the bath a discharge port 3., is provided having its lower lip just above the level of the bath. The expanded cork granuies as they emerge from the lead bath are pushed by the plates and directed through the discharge port ll, into a discharge hopper nowhere they are accumulated until a suillcient amount is collected for the next step. It will be understood, however, that the particles may be fedcontinuously to the next operating means if desired. Upon leaving the bath the cork pieces may take with them mechanically held particles of lead. In order to remove the lead the expanded cork pieces are nowtransierred, preferably by gravity, to a storage hopper 34, positioned above a conveyor II which carries the particles to a grinder 38, where the cork pieces are divided into the desired sizes and fed toa screen- 4|, which permits the desired sizes to pass therethrough and retains the oversize particles which are returned by the means 42, to the grinder for "reprocessing. The particles passing through the screens are dropped into a separation Y tank 44 containing water and the lead particles having been loosened from the cork pieces in the grinding and screening process readily fall to the bottom of the tank .bath comprises a In this example either apparatus and procedure Example No. 1' mayalso be employed.

nt of the 'cork pieces is, howthree minutes and the metallic molten alloy consisting of 20% than lead (meltingp'oint 572 R).

bath during the treatment is maintained at about 330 C. (626' F). The expanded cork obtained in this caseis not as springy as that in Example No. 1 and crushes more readily, but. is not of a brittle nature. When ground toa size passing a 12 mesh screen the density is found to be -l.51-pounds per cubic foot. In this case about 40% distillate is obtained based upon the weight of thenatural late contains about 50% of aqueous material and the remainder is a waxy oily material which separates with diiilculty. when treated with strong caustic, the oily material is dissolved and a yellowish brown wax is precipitated which can be separated. This waxy material decomposes when heated to its boiling point and from its general seem to be related to the cork waxes, cerin and friedelin, more generally referred to as cork alcoho From the above examples it will be understood that various mediums cork treatment. Moreover,

as used in v The timeof trea ever, increased to it will be unders period of submersion cork used. This distilmay be employed for the s obtained by ever specific movedJrom the cork are responsible for the obtaining of the waxysuhltlncc which is-apparobtained. while waxes have been extracted from cork by expensive solvent extracti none has ever to my knowledge been heat treatment of cork. Accordingly, theprocessingfor obtaining by-products such as the primary waxy a further and additional feature of the present invention.

From the foregoing description it will be seen that I have presented a new and novel process of expanding cork pieces, that I have produced a cork material of exceedingly low density and that may be non-brittle, soft, rubbery and springy; that I have discovered a procedure for producing cork distillates that eliminates steps heretofore substance constitutes --with removal of volatiles including decomposifound necessary in my prior procedures, and that Y I have discovered a process of obtaining cork pieces oi exceptional low density that may or may not possess fungus growth inhibiting properties. The new process is simple, practical, readily con-q trolled, and economical in its-operation. It will be appreciated that various departures from the specifically disclosed procedure will occur to those skilled in the art without departure from the letter and spirit of the present invention. For example, the heat treatment may be carried out in several steps and the raw cork at the beginning of the process may not be a natural cork. Accordingly, it is desired that the present invention be construed to include all equivalents and as broadly as the following claims taken in conjunction with the prior art may follow. Whenvalues are given for densities of the new cork product throughout the specification and in the claims, it is intended that these are densities of the cork when ground to a size passing a 12 mesh screen and retained on a 50 mesh screen. However, it is to be understood that fines of a size smaller than 50 and pieces greater than 12 are not outside the scope of the present invention, the figures given being intended solely as a guide for testing densities.

I claim:

l. The process or making low density cork" pieces adapted for insulation and the like, comprising providing a multiplicity of cork pieces to be treated, submerging said cork pieces in and in direct contact with a liquid medium substantially non-absorbent and non-adherent with respect to cork, and having a temperature between 580 F. to 720 F. and maintaining said cork pieces in said liquid medium for a total period not exceeding about four minutes.

2. A process as in claim 1 wherein the temperature of the liquid medium is between about 620 F. to about 680 F.

3. A process as in claim 1 wherein the temperature of the liquid medium is between 620 F. to about 655 F.

4. A process as in claim 1 wherein the liquid medium is a molten metallic one.

5. The process of making low density cork pieces adapted for insulation and the like, comprising treating a multiplicity of cork pieces having a density not under about 5 pounds per cubic foot by submersion, in a condition in which the cork is free to expand without restriction,

in and in direct contact with a molten lead bath having a temperature sufllciently high but not under 580 F. and not over 120 F. for a total period of time not exceeding about four minutes to obtain individual cork pieces havin a density between about 1 /2 to 3 pounds per which the cork is free material in amount tion material, and grinding said cork pieces to a size passing through a number 12 mesh screen,

.saidvcork having a density between about 1 /2 to 3 pounds per cubic foot.

' 7. The process of making low density cork pieces adapted for insulation and the like, comprising submerging cork pieces substantially between M1 to A; inch in size, in-a condition in to expand without restriction, in aiid'in direct contact with a molten metallic bath having a temperature between about 620 F. to about 680 F. for a total period between about 40 seconds to about 3 minutes.

8. The process of making low density cork pieces adapted for insulation and the like, comprising submerging natural cork pieces in and in direct contact with a molten metallic bath having a temperature between about 620 F. to about 680 F. for a total period of time in the order of about 40 seconds to effect a rapid expansion of the cork pieces in amount exceeding about 200% by volume and loss of volatiles in amount not exceeding about 15% by weight of the natural cork.

9. The process of making low density cork pieces'adapted for insulation and the like, comprising submerging natural cork pieces in and in direct contact with a molten metallic bath having a temperature between about 620 F. to about 680 F. for a total period of time not exceeding about 4- minutes, whereby to effect a rapid expansion oi" the cork pieces in an amount at least between 200'to 375% by volume and a removal of volatiles and decomposition exceeding 15% but substantially no greater than 40% by weight of the natural cork.

sis

10. The process of making low density regranulated cork comprising preparing natural cork ranules between about V4 inch to about /2 inch in size, submerging said cork granules in and in direct contact with a liquid metallic bath comprising lead maintained at a temperature between about 620 F. to about 680 F., treating said cork granules fora total period of submergence between about 40 seconds to about 4 minutes to eflect a rapid expansion of the cork granules together with removal of volatiles and decomposition material, whereby to obtain individual cork granules having a volume increase between about 200 to 375% and a loss of volatiles and decomposition material between about 15% to about 40% by weight of the natural cork, and comminuting said cork granules to a size passing a 12 mesh screen to produce regranulated cork having a density between about 1 to about 2% pounds per cubic foot.

11. The process of making low density cork pieces adapted for insulation and the like, comprising treating cork pieces in boiling water to effect a partial absorption of moisture therefrom,

said whiter trccted cork Piece; conmature between 500', r. to 720' a, maintain in and cor: piecain said medium for a total period not exceeding about 4 minutes to obtain cmnn'ms m scmmf 

